Such films are used hermetically to seal and protect products inside the container from exposure to the atmosphere. Generally such films and packaging are formed from plastics such as PET Mylar OLAF. However, it is well known that plastic packaging materials derived from such plastic based materials pose various environmental issues in that they are not biodegradable nor formed from renewable sources.
On the other hand, PLA and biopolymer based packaging materials are particularly attractive as sustainable alternatives to petrochemical-derived plastic products, since the materials from which they are derived are from renewable sources. In the case of PLA for example, the lactate from which PLA is ultimately produced can be derived from the fermentation of agricultural by-products such as corn starch or other starch-rich substances like maize, sugar or wheat. PLA therefore provides an environmentally friendly alternative to petrochemical based plastics in that they are biodegradable and can be manufactured from renewable sources. Other suitably rigid container-forming materials which have been proposed include other biodegradable starch-based materials, cellulosic materials and biodegradable synthetic materials.
Containers made from rigid PLA based materials are typically formed with an open top which is then sealed with a film lid to enclose the contents in the container. To open the container the lid is peeled from the container; the lid and container are eventually discarded. Filmic lids for attaching to such containers suffer from a number of problems, such as providing adequate strength of seal between the filmic lid and the container and misting of the filmic lid following sealing with the container.
The adhesion of the film coating to the container when wet can lead to stringing and/or peeling of the coating. In addition certain materials are only suitable for sealing container openings no longer than 10 cm. Also, weld sealing can occur, causing the film to break or tear in the seal area, creating inconvenience for the consumer opening the pack.
Currently, a coated PET film Mylar OLAF provides the best performance in terms of peel seal and anti-misting properties. However, such filmic lids are not biodegradable and are not manufactured from renewable sources.